arXiv:0907.1211v1 [astro-ph.IM] 7 Jul 2009 RCEIG FTE31 THE OF PROCEEDINGS hwrrcntuto n akrudrjcinpower the rejection telescopes, background both and telescope with simultane- reconstruction showers the i.e. shower air mode, of observing observation performance stereo ously In expected [3]. the system study to MeV 100 TeV. between 10 in range energy and phenomena wide energy the high in Universe the the of studies will detailed satellite allow FERMI the with observations Simultaneous esitrne hc slmtdb h bopinof absorption accessible the the by limited extend is energy and an high which have studies range, will pulsar redshift telescopes on two MAGIC impact the energy increased lower of expected an threshold The from instrument. the benefit of will sensitivity physics astrophysics from fundamental ranging to collaboration MAGIC the by threshold. energy simul- the sensitivity and lower improved mode taneously telescope an operation achieve two stereoscopic/coincidence to in The the designed electronics. is by photon system, advanced readout upgraded with been and telescope 2004. has detectors twin summer MAGIC a of since years and construction operation past altitude m the scientific 2200 In in at Palma been La Muchachos has los Island de Canary Roque the the at exist- on installed among as- is threshold It ray IACTs. energy gamma ing lowest energy the high with very tronomy for Cherenkov Atmospheric (IACT) Imaging telescope dish single largest the reported. first be the and will of telescopes performance MAGIC-II technical two combined of the elements of the results hardware of of the description update a all 2008. MAGIC-I, An of of MAGIC-I. performance technical with end integration the elements commissioning and undergoing by technical currently is installed the telescope The were All MAGIC-II a readout. and of fast transmission GSps area, signal trigger 2-4 analog wider a optical with improved namely camera improvements, pixelized significant but highly MAGIC-I, a of of number clone a a with stereo- is in MAGIC-II MAGIC-II, MAGIC-I mode. with telescope, scopic coincidence second in A operate tele- world. will the Cherenkov in Atmospheric scope Imaging single-dish ealdMneCrosuishv enperformed been have studies Carlo Monte Detailed l set ftewd hsc rga addressed program physics wide the of aspects All today of as is telescope [1] MAGIC diameter 17m The Keywords Abstract unCortina Juan h AI- eecp stelargest the is telescope MAGIC-I The . γ AI,VE performance. VHE, MAGIC, : ry yteetaaatcbcgon light. background extragalactic the by -rays ehia efrac fteMGCTelescopes MAGIC the of Performance Technical .I I. ∗ ntttd iiadAtsEege,Crayl e Valles del Cerdanyola Energies, d’Altes Fisica de Institut NTRODUCTION ∗ lra Goebel Florian , † st a-lnkIsiu f Max-Planck-Institut CC Ł ICRC, OD ´ 2009 Z ´ † hmsSchweizer Thomas , rPyi,D885M D-80805 Physik, ur ¨ cp ihraoal fot.Lre m 1 Larger efforts. tele- new reasonable the with most of scope or potential reliability physics increased improved importantly reduction, cost allow they alerts. any GRB to to seconds reaction 30-60 fast within for reposition telescopes position sky to Both marginally able telescope. only be first are will the (AMC) of copies control and improved [2] rein- mirror system fiber active drive the carbon the frame, lightweight telescope of plastic The clone forced telescope. a parameters first fundamental MAGIC the most second in the is production telescope and design for a required telescope. at first installed the from been telescopes m has 85 two of the telescope distance of MAGIC distance second the the on dependence sensitivity moderate the showing study of results MC the dedicated Following a and GeV. of range 100 energy below whole the larger to over 2 foreseably expected analysis of factor is better a reduced sensitivity by increase a an overall The and in threshold. resolution energy results energy This and improved. angular significantly are The right. 2008. the Summer hardware on in drive installed and seen were control be mirror active can mirrors, frame, telescope 2004. The since second 2009. regularly operates April The left, in the telescopes on telescope, MAGIC first two The 1: Fig. ht eetr HD) nfr aeawt 1039 with hybrid camera QE uniform 0.1 high A identical (HPDs). with modular detectors upgrades a photo allows while efficiency design (PMTs), quantum camera tubes camera increased the photomultiplier with phase (QE) equipped first and been the rates In has sampling consumption. fast power ultra low MAGIC- features developed system newly readout II The efforts. cost reducing installation MAGIC-II and for developed been have ments el eeoe opnnsaeepoe whenever employed are components developed Newly resources the and time the minimize to order In † o h AI Collaboration MAGIC the for , nhn Germany unchen, ¨ o edo iw(o)pxl sefiueII) figure (see pixels (FoV) view of field -89 Spain E-08193 , 2 irrele- mirror 1 2 JUAN CORTINA et al. TECHNICAL MAGIC

allows an increased trigger area compared to MAGIC-I. 1000 927 1001 928 834 1002 929 835 833 1003 930 836 738 926 1004 931 837 739 832 1005 932 838 740 737 925 1006 933 839 741 647 831 999 The entire signal chain from the PMTs to the FADCs 1007 934 840 742 648 736 924 935 841 743 649 646 830 998 936 842 744 650 562 735 923 937 843 745 651 563 645 829 997 938 844 746 652 564 561 734 922 939 845 747 653 565 483 644 828 996 846 748 654 566 484 560 733 921 is designed to have a total bandwidth as high as 500 847 749 655 567 485 482 643 827 995 848 750 656 568 486 410 559 732 920 849 751 657 569 487 411 481 642 826 994 752 658 570 488 412 409 558 731 919 753 659 571 489 413 343 480 641 825 993 754 660 572 490 414 344 408 557 730 918 850 661 573 491 415 345 342 479 640 824 992 MHz. The Cherenkov pulses from γ-ray showers are 662 574 492 416 346 282 407 556 729 917 755 575 493 417 347 283 341 478 639 823 851 576 494 418 348 284 281 406 555 728 916 940 663 495 419 349 285 227 340 477 638 822 756 496 420 350 286 228 280 405 554 727 915 852 577 421 351 287 229 226 339 476 637 821 941 664 422 352 288 230 178 279 404 553 726 914 very short (1-3 ns). The parabolic shape of the reflector 757 497 353 289 231 179 225 338 475 636 820 853 578 354 290 232 180 177 278 403 552 725 942 665 423 291 233 181 135 224 337 474 635 819 1008 758 498 292 234 182 136 176 277 402 551 724 854 579 355 235 183 137 134 223 336 473 634 818 943 666 424 236 184 138 98 175 276 401 550 723 of the MAGIC telescope preserves the time structure of 1009 759 499 293 185 139 99 133 222 335 472 633 855 580 356 186 140 100 97 174 275 400 549 722 944 667 425 237 141 101 67 132 221 334 471 632 1010 760 500 294 142 102 68 96 173 274 399 548 913 856 581 357 187 103 69 66 131 220 333 470 817 945 668 426 238 104 70 42 95 172 273 398 721 1011 761 501 295 143 71 43 65 130 219 332 631 912 the light pulses. A fast signal chain therefore allows one 857 582 358 188 72 44 41 94 171 272 547 816 946 669 427 239 105 45 23 64 129 218 469 720 991 1012 762 502 296 144 46 24 40 93 170 397 630 911 858 583 359 189 73 25 22 63 128 331 546 815 947 670 428 240 106 26 10 39 92 271 468 719 990 1013 763 503 297 145 47 11 21 62 217 396 629 910 859 584 360 190 74 12 9 38 169 330 545 814 to minimize the integration time and thus to reduce the 948 671 429 241 107 27 3 20 127 270 467 718 989 1014 764 504 298 146 48 4 8 91 216 395 628 909 860 585 361 191 75 13 2 61 168 329 544 813 1039 949 672 430 242 108 28 1 37 126 269 466 717 988 1015 765 505 299 147 49 5 19 90 215 394 627 908 861 586 362 192 76 14 7 60 167 328 543 812 1038 950 673 431 243 109 29 6 36 125 268 465 716 987 influence of the background from the light of the night 766 506 300 148 50 15 18 89 214 393 626 907 862 587 363 193 77 30 17 59 166 327 542 811 1037 951 674 432 244 110 51 16 35 124 267 464 715 986 767 507 301 149 78 31 34 88 213 392 625 906 863 588 364 194 111 52 33 58 165 326 541 810 1036 952 675 433 245 150 79 32 57 123 266 463 714 985 768 508 302 195 112 53 56 87 212 391 624 905 sky (LONS). In addition a precise measurement of the 864 589 365 246 151 80 55 86 164 325 540 809 1035 676 434 303 196 113 54 85 122 265 462 713 984 769 509 366 247 152 81 84 121 211 390 623 904 865 590 435 304 197 114 83 120 163 324 539 808 1034 677 510 367 248 153 82 119 162 264 461 712 983 770 591 436 305 198 115 118 161 210 389 622 903 678 511 368 249 154 117 160 209 323 538 807 1033 time structure of the γ-ray signal can help to reduce the 771 592 437 306 199 116 159 208 263 460 711 982 866 679 512 369 250 155 158 207 262 388 621 902 772 593 438 307 200 157 206 261 322 537 806 1032 867 680 513 370 251 156 205 260 321 459 710 981 773 594 439 308 201 204 259 320 387 620 901 868 681 514 371 252 203 258 319 386 536 805 953 774 595 440 309 202 257 318 385 458 709 980 background due to hadronic background events [9]. 869 682 515 372 253 256 317 384 457 619 900 954 775 596 441 310 255 316 383 456 535 804 870 683 516 373 254 315 382 455 534 708 979 955 776 597 442 311 314 381 454 533 618 899 871 684 517 374 313 380 453 532 617 803 956 777 598 443 312 379 452 531 616 707 Both telescopes can be seen in figure 1. The frame of 1016 872 685 518 375 378 451 530 615 706 898 957 778 599 444 377 450 529 614 705 802 1017 873 686 519 376 449 528 613 704 801 958 779 600 445 448 527 612 703 800 1018 874 687 520 447 526 611 702 799 897 959 780 601 446 525 610 701 798 896 1019 875 688 521 524 609 700 797 895 MAGIC-II and a fraction of the mirrors were installed 960 781 602 523 608 699 796 894 1020 876 689 522 607 698 795 893 978 961 782 603 606 697 794 892 977 1021 877 690 605 696 793 891 976 962 783 604 695 792 890 975 1022 878 691 694 791 889 974 963 784 693 790 888 973 1031 back in 2007. The remaining hardware was installed in 1023 879 692 789 887 972 1030 964 785 788 886 971 1029 880 787 885 970 1028 965 786 884 969 1027 881 883 968 1026 882 967 1025 the Summer 2008. The telescope is currently undergoing 966 1024 extensive tests and integration with MAGIC-I. The sys- tem of two telescopes will end its commissioning phase Fig. 2: A scheme of the MAGIC-II camera. Only colored in Fall 2009. pixels in a round configuration will be equipped. The The telescopes have been recently renamed “MAGIC hexagonal shapes indicate the trigger region, which is Florian Goebel Telescopes” in memory of the project almost twice as large as the trigger region of the first manager of MAGIC-II, who died shortly before com- telescope. pleting the telescope in 2008. In the following the main technical features of the sec- ond telescope and several upgrades to the first telescope are discussed. References to more detailed contributions to the same conference are provided. A description of the performance of the two telescope system will be presented at the conference.

II. MIRRORS Like in MAGIC-I the parabolic tessellated reflector consists of about 250 individually movable 1 m2 mirror units, which are adjusted by the AMC depending on the orientation of the telescope. While in MAGIC-I each mirror unit consists of 4 individual spherical mirror tiles mounted on a panel, MAGIC-II is equipped with 1 m2 spherical mirrors consisting of one piece. This reduces Fig. 3: A view of the MAGIC-II camera from the back cost and manpower because it is no longer necessary to shortly after its physical installation at the site and before align all four mirrors individual tiles inside one panel plugging in the 7-pixel clusters. The 169 cluster modules before installing the panels at the telescope. are inserted from the camera front into the square holes Two different technologies have been used for the pro- which can be seen on the support metal plate. The 2 duction of the 1 m mirrors. Out of the 247 mirror tiles, pixel signals are transfered to the control house through 143 are all-aluminum mirrors consisting of a sandwich optical fibers bundled inside the outer black cable ducts. of two 3 mm thick Al plates and a 65 mm thick Al honeycomb layer in the center. During production the sandwich is already bent into a spherical shape, roughly with the final radius of curvature. The polishing of the show a PSF which almost doubles (∼6 mm) that of the mirror surface by diamond milling is done by the LT all-Al mirrors but the light spot is still well inside the Ultra company. Finally, a protecting quartz coating is size of a camera pixel. applied. The reflectivity refl and the radius R90 of III. CAMERA the circle containing 90% of the spot light have been measured to be around refl = 87% and R90 = 3 mm. A modular design has been chosen for the camera of The remaining 104 mirror tiles are produced as a the MAGIC-II telescope [4]. Seven pixels in a hexagonal 26 mm tick sandwich of 2 mm glass plates around a Al configuration are grouped to form one cluster, which honeycomb layer using a cold slumping technique. The can easily be removed and replaced. This allows easy frontal glass surface is coated with a reflecting Al layer exchange of faulty clusters. More importantly, it allows and a protecting quartz coating. The glass-Al mirrors full or partial upgrade with improved photo detectors. PROCEEDINGS OF THE 31st ICRC, ŁOD´ Z´ 2009 3

The 3.5o diameter FoV is similar to that of the MAGIC- I camera. The MAGIC-II camera is uniformly equipped with 1039 identical 0.1o FoV pixels in a round config- uration (see figures II and II). In the first phase increased QE PMTs have been installed. The Hamamatsu R10408 6 stage PMTs with hemispherical photocathode typically reach a peak QE of 34%. The PMTs have been tested for low afterpulsing rates, fast signal response (∼1 ns FWHM) and accept- able aging properties. Fig. 4: Microphotograph of the Domino chip (left) and Hamamatsu delivers PMT modules which include a inside the package (right). socket with a Cockcroft-Walton type HV generator. The PMT socket and all the front-end analog electronics is assembled to form a compact pixel module. The broad- band opto-electronic front-end electronics amplifies the under construction. The readout will also be upgraded PMT signal and converts it into an optical pulse, which to a digitizing system similar to that of MAGIC-II (see is transmitted over optical fibers to the counting house. below). A cluster consists of 7 pixel modules and a cluster IV. READOUT body which includes common control electronics, power distribution and a test-pulse generator.On the front side The optical signals from the camera are converted the PMTs are equipped with Winston cone type light back to electrical signals inside the counting house[10]. guides to minimize the dead area between the PMTs. The electrical signals are split in two branches. One The slow control electronics sets the pixel HV and reads branch is further amplified and transmitted to the digitiz- the anode currents, the HV values and the temperature ers while the other branch goes to a discriminator with of each pixels. It is in turn controlled by a PC in a software adjustable threshold. The generated digital the counting house over a custom made RS485 and signal has a software controllable width and is sent to the VME optical link. The camera control software[5] is trigger system of the second telescope with a software programmed in Labview and can be remotely steered adjustable time delay. Scalers measure the trigger rates by a central computer[8]. of the individual pixels. The calibration system of MAGIC-II[7] is based on a The new 2 GSamples/s digitization and acquisition frequency tripled passively Q-Switched Nd-YAG laser, system is based upon a low power analog sampler operating at the third harmonic at 355 nm, which has called Domino Ring Sampler (see figure: 4). The analog been installed in the center of the mirror dish. The signals are stored in a multi capacitor bank (1024 cell pulse width at 355nm is 700ps. For providing a large in DRS version 2) that is organized as a ring buffer, in dynamic range we are using two rotating filter wheels which the single capacitors are sequentially enabled by under computer control that allow one to illuminate the a shift register driven by an internally generated 2 GHz camera with intensities within 100 steps from single to clock locked by a PLL to a common synchronization 1000 photoelectrons. MAGIC-I will be equipped with a signal. Once an external trigger has been received, the similar system in the next months. sampled signals in the ring buffer are read out at a The flexible cluster design allows field tests of this lower frequency of 40 MHz and digitized with a 12 bits new technology within the MAGIC-II camera without resolution ADC. major interference with the rest of the camera. The first Data management is performed by 9U VME digital test will in fact take place in the next months: it is boards which handle the data compression and refor- planned to equip six 7-pixel modules in the outermost matting as well. Every board hosts 80 analog channels ring of MAGIC-II with HPDs [6] (at the corners of the plus auxiliary digital signals for trigger and monitor hexagon in figure II which are not instrumented with purposes. For a 1 kHz trigger rate and a 2 GHz frequency PMTs). These HPDs feature peak QE values of 50%. sampling, the data throughput can be as high as 100 The smaller trigger area and somewhat lower light MBytes/s thus being a challenge for modern data trans- conversion efficiency of the first MAGIC telescope will mission and storage solutions. The data are transferred limit the performance of the telescope system. This to PCI memory via Gbit optical links using the CERN justifies a recent decision to upgrade the camera of S-link protocol and to the mass storage system[11]. MAGIC-I. The new MAGIC-I camera will be a clone The MAGIC I telescope produces currently per year of the camera of MAGIC-II, i.e., will have an increased 100TByte of raw data that is calibrated and reduced trigger area and will be fully equipped with 0.1o FoV on-site. Since 2007 most of the the data has been pixels. However its inner section (about 400 pixels) may stored and further processed at the official MAGIC- be readily equipped with HPDs, i.e. the sensitivity of the II datacenter at PIC, Barcelona[12]. This datacenter is new camera would significantly increase for low energy currently undergoing an upgrade to accomodate the even showers. The camera frame and electronics are already larger storage demands of MAGIC-II. 4 JUAN CORTINA et al. TECHNICAL MAGIC

The newest version of the DRS chip (DRS version 4) features a number of advantages over DRS-2, so work is underway to upgrade the system in the next year to DRS-4.

V. TRIGGER The trigger system of the second telescope like the trigger of the first telescope[13] is based on a compact next neighbor logic. However, the uniform camera de- sign allows an increased trigger area of 2.5o diameter FoV. This increases the potential to study extended sources and to perform sky scans. When the two telescopes are operated in stereo mode a coincidence trigger (so-called “level 3” trigger) between the two telescopes rejects events which only triggered one telescope. In order to minimize the coincidence gate in the level 3 trigger, the triggers produced by the individual telescopes will be delayed in a time which depends of the geometry of the telescopes. This will reduce the overall trigger rate to a rate which is manageable by the data acquisition system. Starting in 2007, an additional trigger runs in parallel with the standard next neighbour trigger in first tele- scope. This so-called “sumtrigger” [14] operates on the analog sum of groups of 18 pixels and has allowed to lower the trigger threshold of the MAGIC telescope by a factor of two to 25 GeV.

VI. ACKNOWLEDGMENTS We would like to thank the IAC for excellent working conditions. The support of the German BMBF and MPG, the Italian INFN and the Spanish MICINN, the Swiss ETH and the Polish MNiI is gratefully acknowledged.

REFERENCES [1] E. Lorenz, New Astron. Rev. 48 (2004) 339; [2] T. Bretz et al., Astropart. Phys. 31 (2009) 92. [3] P.Colin, et al., “Performance of the MAGIC telescopes in stereo- scopic mode”,these proc.; [4] D. Borla-Tridon, et al., “Performance of the Camera of MAGIC II Telescope”, these proc. [5] B. Steinke et al., “MAGIC-II Camera Slow Control Software”, these proc.; [6] R. Orito et al., “Development of the HPD Cluster for MAGIC- II”, these proc.; [7] J. Hose et al., “Calibration of the MAGIC Telescopes”, these proc.; [8] R. Zanin et al., “The Central Control of the MAGIC telescopes”, these proc.; [9] E. Aliu et al., Astropart. Phys. 30 (2009) 293; [10] D. Tescaro et al., “The readout system of the MAGIC-II Cherenkov telescope”, these proc.; [11] E. Carmona et al., “A Flexible High Demand Storage System for MAGIC-I and MAGIC-II usign GFS”, these proc.; [12] I. Reichardt et al., “The MAGIC DataCenter”, these proc.; [13] D. Bastieri et al., Nucl. Instrum. Meth. A, 461 (2001) 521; [14] N. Otte et al., “A new analog sum trigger for the MAGIC telescope provides a trigger threshold at 25 GeV”, these proc.;